Some instinctive social behaviors of the wolf may be left unexpressed in the dog simply because the opportunity never arises for them to be expressed in a new social setting. But even when dogs range freely in wild or semi-wild circumstances, they show distinct divergences from their wild ancestors. As part of his behavioral study of the wolf, Erik Zimen raised a pack of poodles and a pack of wolves under quite similar conditions. While the wolves ran free inside an enclosure, the poodles had free run of the rest of the property.

Zimen and his colleagues recorded 362 specific behaviors displayed by wolves, everything from yawning and stretching to howling and tail wagging. The poodles displayed 64 percent of those behaviors with little or no change. About 13 percent of wolf behaviors had vanished altogether, and 23 percent persisted but in markedly modified form. Zimen found that in performing many of these modified behaviors, the poodles lacked a seriousness of purpose; compared to the wolves, the poodles were more playful or simply inept. As Raymond Coppinger observed with his village dogs, Zimen's poodles were incapable of hunting large prey. The poodles readily chased things, but their choice of "prey" was indiscriminate - birds, leaves, bicyclists - and it was clearly a game, an end in itself, very much as with young wolves at play.

The most striking differences seen in the poodles was in their expressive behavior or rather, lack thereof. Wolves exhibit a rich array of facial expressions, ear movements, tail positions, and body postures. In poodles many of these expressions were greatly simplified, and many were absent altogether. The lip curling, snarling, and baring of teeth displayed routinely by wolves in defensive and aggressive situations was considerably muted and simplified in poodles. In part, this is simply because poodles are generally less fearful and less aggressive and tend not to mind invasions of personal space as much as wolves do: they just have less of an impulse to act annoyed. Starting as early as four weeks, wolf cubs begin to sleep
apart from one another more and more often. By the time the cubs are four to six months old, they are like adult wolves, and almost never make contact with another wolf when sleeping.

The poodles, however, continued to frequently lie together through the age of eight months or older, and even as full-grown adults did so about a third of the time, and even in hot weather when there was no conceivable reason for huddling to preserve body heat. Dogs are, in other words, simply more pacific and easygoing by nature.

Studies of poodle-wolf hybrids suggest that there may be more than one behavioral component to dogs' milder dispositions. When Zimen recrossed poodle-wolves ("puwos") together, these second-generation hybrids came in a mixed assortment of behavioral types. Some were timid about approaching humans but were very affectionate when they did; others were tame and not disposed to flee from novelties but were emotionally aloof. Zimen suggests that a reduction in the flight instinct and a greater capacity for socialization and bonding may be separately inherited traits, though both are necessary for wolves to become dogs.